1. Field of the Invention
The present invention relates generally to a binding device configured to perform a sheet-bundle binding process by bringing two rotary members, each including a serrated portion formed on an outer circumferential surface of the rotary member, into engagement with each other with a sheet bundle pinched therebetween, and an image forming apparatus such as a copier, a printer, a facsimile, or a multifunction circumferential having two or more of a copier function, a printer function, and a facsimile function including the binding device.
2. Description of the Related Art
A known type of binding devices mounted on an image forming apparatus such as a copier or a printer includes serrated portions and binds a sheet bundle made up of a plurality of sheets by pressing the serrated portions against the sheet bundle to form serrations in the sheet bundle in the thickness direction and bring the sheets into engagement with each other, thereby performing a binding process without using a metal staple. An example of such a binding device is disclosed in Japanese Patent No. 5253453.
More specifically, the binding device disclosed in Japanese Patent No. 5253453 includes two rotary members each including a serrated portion (i.e., having a serrating embossing profile) formed all around the outer circumferential surface of the rotary member. The binding device performs a binding process on a desired area of a sheet bundle (a bundle of a plurality of sheets) by rotating the two rotary members with the sheet bundle pinched therebetween to form serrations in the sheet bundle while moving the sheet bundle in a moving direction which lies along a rotating direction of the two rotary members.
Japanese Laid-open Patent Application No. 2013-180883 discloses a technique implemented as a binding device that performs a sheet-bundle binding process by bringing serrated portions, each formed on one of facing surfaces of two nonrotary members, into engagement with each other with a sheet bundle pinched therebetween. The binding device includes a sheet pressing member that holds the sheet bundle being bound to prevent the sheet bundle from becoming untidy in the binding process.
However, such a conventional binding device has a disadvantage that, when performing a sheet-bundle binding process by bringing two rotary members, each including a serrated portion formed on its outer circumferential surface, into engagement with each other with a sheet bundle pinched therebetween, the serrated portions pull the sheet bundle in a moving direction which lies along a direction in which the rotary members rotate, thereby distorting the sheet bundle. As a result, the sheets of the sheet bundle that have become untidy are bound unfavorably in terms of appearance.
As can be seen, there is a need for a binding device that, even when performing a sheet-bundle binding process by bringing two rotary members, each including a serrated portion formed on the outer circumferential surface of the rotary member, into engagement with each other with a sheet bundle pinched therebetween, is less likely to cause a problem that sheets of the sheet bundle become untidy and are bound unfavorably in terms of appearance, and an image forming apparatus including the binding device.